1. Field of the Invention
Aspects of the present invention relate to a thin film transistor, a method of fabricating the same, and an organic light emitting diode (OLED) display device including the same. More particularly, aspects of the present invention relate to a thin film transistor that can prevent leakage current by removing crystallization inducing metals from a channel region of a semiconductor layer, reduce an edge effect by automatically forming source-body contact and eliminating a kink effect, a method of fabricating the same, and an OLED display device including the same.
2. Description of the Related Art
Flat panel display devices, such as, for example, liquid crystal display (LCD) devices, OLED display devices and plasma display panels (PDP), have been receiving a lot of attention, since such devices overcome disadvantages (such as heavy weight and large size) of conventional display devices such as cathode ray tubes.
OLED display devices have advantages over LCDs and PDPs. Since LCDs are passive devices and not self-emissive devices, there are limits to their brightness, contrast, viewing angles, large size, and so on. While PDPs are self-emissive devices, they are heavier, consume more power, and are more complicated to make than other flat panel displays. By contrast, since OLED display devices are self-emissive devices, they have an excellent viewing angle and contrast. Also, since OLED display devices do not need a backlight, they can be made thin and lightweight, and consume less power.
Moreover, OLED display devices have advantages such as being driven by direct current at low voltage, a fast response time, durability against external impact because they are formed entirely of solids, wide operating temperatures, and being manufactured by simple and economical methods.
Flat panel display devices such as OLED display devices or LCD devices use a thin film transistor as a switching device or a driving device.
FIG. 1A is a plan view of a conventional thin film transistor, and FIG. 1B is a cross-sectional view taken along line I-I of FIG. 1A. Referring to FIGS. 1A and 1B, in the conventional thin film transistor, a buffer layer 101 is disposed on a substrate 100, which is formed of glass or plastic, and a semiconductor layer 102, including source and drain regions 102a doped with impurities and a channel region 102b interposed therebetween, is disposed on the buffer layer 101.
In addition, a gate insulating layer 104 is disposed on the semiconductor layer 102, a gate electrode 105 is disposed to correspond to the channel region 102b of the semiconductor layer 102 on the gate insulating layer 104, and an interlayer insulating layer 107 is disposed on the gate electrode 105. Contact holes 108 exposing a predetermined region of the semiconductor layer 102 are formed, and source and drain electrodes 109 filling the contact holes 108 and electrically connected to the predetermined regions of the semiconductor layer 102 are disposed on the interlayer insulating layer 107.
Although it is desirable to remove elements from a thin film transistor that suppress its characteristics such as an edge effect to serve as a driving device for the flat panel display device, it may be difficult to solve these problems structurally in a conventional thin film transistor.
Moreover, a method of crystallizing an amorphous silicon layer into a polycrystalline silicon layer using a crystallization inducing metal, such as a metal induced crystallization (MIC) method or metal induced lateral crystallization (MILC) method, causes the thin film transistor to be subject to a leakage current because of the remaining crystallization inducing metals on the semiconductor layer.